phy: rockchip: usbdp: Adopt driver to work with upstream DT

The upstream DT binding added in linux-phy next commit a75d8056e9fe
("dt-bindings: phy: add rockchip usbdp combo phy document") does not
define subnodes for the type of PHY, instead it is expected that phandle
args are used for setting the type of the PHY.

  phys = <&usbdp_phy0 PHY_TYPE_USB3>

Adopt the usbdp phy driver to work with upstream DT binding targeted for
Linux kernel v6.10.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>